Bird of the Week – Antarctic Tern ~ by Ian Montgomery
Newsletter – 8-28-12
I’ve been adding photos from the recent Hong Kong, Finland, Ireland trip to the website and have encountered a few that are also on the Australian list such as the Arctic Tern. That was my initial choice for this week’s bird until I changed it to the closely related but lesser known Antarctic Tern as I took some photos of it on the Sub-Antarctic Islands trip last November that I would like to share. It is also on the Australian list and breeds at Macquarie and Heard Islands, though it is regarded as a very rare vagrant to the mainland.
We first encountered them at Snares, on the day after leaving Dunedin, first photo. Snares is a nature reserve and we weren’t allowed to land there but, as you can judge from the photo, weather conditions were good and we could get very close to some of the birds and mammals in the Zodiacs. This bird is in breeding plumage and the coral red bill and leg colour is sufficient to distinguish it from the similar breeding Common and Arctic Terns, both of which spend the northern winter in the southern hemisphere. These two breed in the northern hemisphere in the northern summer and both the time of the year and the location are also sufficient circumstantial evidence to eliminate birds of those species in breeding plumage. Apart from that, there are other subtler differences relating to size, plumage and proportions with the Antarctic Tern being both larger and stockier than the other two.
Some of these difference, such as the extent of transparency and dark webs in the flight feathers can only be seen in flight, second photo. If you’re not too worried about identification, then you can appreciate the beauty of all these elegant mid-sized terns and, given their graceful flight and forked tails, it’s no wonder that they have been called Sea Swallows. This photo was taken the following day at Enderby Island, one of the Auckland Islands. We were allowed to land there and it proved to be a fascinating place. At a small colony of nesting Antarctic Terns the bird in the third photo is just landing at its neat grassy nest to incubate the two eggs.
Both at Snares and on Enderby, there were other similar terns in non-breeding plumage, fourth photo, hanging around the edges of the breeding colony. This is where separation of the three species gets tough and is either a fascinating challenge or a nightmare for keen birders – depending on one’s attitude – and it’s no surprise that in the British Isles Common and Arctic Terns are collectively and wryly referred to as ‘Comic’ Terns. Birders have it fairly easy there and don’t have to worry about Antarctic Terns (we won’t even discuss the South American and Kerguelen Terns which complete the quintet). At Snares, we were tempted to identify this as an Arctic Tern. Arctic Terns, incidentally, easily win the prize for migration, breeding in the higher latitudes of the northern hemisphere and wintering on the coast of Antarctica.
It wasn’t until we got to Enderby and found more of these non-breeding birds in close proximity to breeding Antarctic Terns that we could compare the two sorts side by side and conclude that they were non-breeding Antarctic Terns. When I got home, the Handbook of Birds of the World, confirmed that in some places one year old birds, not old enough to breed, do occur at colonies. It may well be that the few records of Antarctic Terns for mainland Australia is more a reflection of the difficulties of separating non-breeding birds, that their actual rarity.
Back at the website, recent additional species from the trip that might be of interest include:
Ian Montgomery, Birdway Pty Ltd,
454 Forestry Road, Bluewater, Qld 4818
Tel 0411 602 737 firstname.lastname@example.org
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and let birds fly above the earth across the expanse of the heavens. (Genesis 1:20 ESV)
I am glad Ian figures these birds out for us. I have a real challenge just with the Terns I see at our shores. Like Ian tells us, the real ID problem comes when they are in their non-breeding plumages.
Thanks again, Ian, for sharing your birdwatching adventures with us.